Helpful or harmful?
The comradarie between writers can be as positive as it can be negative. I belong to three writing groups, which are each considerably different.
Online and Impersonal
My online writer's group is a small group of approximately eight or so people and it's monitored by a moderator. It's the most limiting group I belong to. They regulate what or how much you post. And it's my least favorite group. I find it strangely perverse for a writer to belong to a writing group, but be censored as to what or how much I write.
The group I've belonged to the longest is another small group with short hour-long meetings. Only ten or so members, but we never all show up at the same meeting, which means there's hardly ever more than 6 or 7 of us there at one time. One of the women brings baked goodies and some are friends outside the group. It's more like a meeting of friends who get onto the conversation of writing. Very supportive and they make great cheerleaders. Many in the group contribute to the local newspaper, but few of them write fiction. In fact, I'm one of the few.
Another group I belong to is one I joined a few months ago. It's the one that I get the most out of. The meetings are supposed to be two hours long, but we find ourselves leaving late every month. And then we stand in groups chatting in the parking lot. Apparently none of us want those meetings to end. We take turns reading chapters or short stories aloud, while the others offer editing suggestions or general comments on what they heard. Each person is asked what they are currently working on or how their latest project is coming along. There are laughs and good times, but the members of this group are seriously dedicated to writing and learning their craft.
As you can see, every group is different. I stick with all three groups because I get something different from each of them and none of them conflict with the others, time-wise.
My suggestion is find what group works for you and your writing. Take suggestions for what they are. Be true to your own writing voice and style. And don't be afraid to move on to another group if you're not getting what you need out of your current one.